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POFread blocks eternally on redirected stdout with named pipes
 

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  1. POFread blocks eternally on redirected stdout with named pipes
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    <p>We are trying to communicate between two processes via named pipes that are redirected to stdin and stdout in the child process. The parent process opens the named pipe and calls fdopen on them. The problem we see is that fwrite on this works, however even reading one byte from redirected stdout pipe blocks eternally. The code works when using the file descriptors instead of FILE *. What is wrong? Code is a little long, sorry.</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include &lt;string.h&gt; #include &lt;unistd.h&gt; #include &lt;fcntl.h&gt; int create_fifo() { int file1; unlink("fifo-0.0"); file1 = mkfifo("fifo-0.0",0666); if(file1&lt;0) { printf("Unable to create a fifo"); return 0; } unlink("fifo-0.1"); file1 = mkfifo("fifo-0.1",0666); if(file1&lt;0) { printf("Unable to create a fifo"); return 0; } return 1; } int main() { int fd, fd0, fd1; pid_t pid; char read_buf_p[50],write_buf_p[50]; char * args[3]; FILE *fd_stdin_p, *fd_stdout_p; create_fifo(); args[0] = "/bin/cat"; args[1] = "-n"; args[2] = NULL; pid = fork(); if(pid == 0) { fd = open("fifo-0.0", O_RDONLY); dup2(fd, 0); close(fd); fd = open("fifo-0.1", O_WRONLY); dup2(fd, 1); close(fd); execv(args[0],args); } else { fd0 = open("fifo-0.0", O_WRONLY); fd_stdin_p = fdopen(fd0,"w"); fd1 = open("fifo-0.1", O_RDONLY); fd_stdout_p = fdopen(fd1,"r"); int sz = fwrite("Hello World", sizeof(char), strlen("Hello World"), fd_stdin_p); fread(read_buf_p,1,1,fd_stdout_p); printf("%s\n", read_buf_p); } return 0; } </code></pre>
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